The invention relates to control of a synchronous meshing type automatic transmission control system coupled to a crankshaft of an internal combustion engine via a clutch, and more particularly, to control for shortening a gear change time.
A method of controlling a synchronous meshing type automatic transmission control system used in a vehicle is disclosed in, for example, Japanese Patent Laid-Open No. 270252/1988. A technique disclosed in this document comprises, in an arrangement, in which a synchronous meshing type automatic transmission control system is coupled to an internal combustion engine via an electromagnetic clutch, controlling a throttle opening so that an amplitude of change between the rotational speed of the internal combustion engine at the time of release of the electromagnetic clutch and the rotational speed of the internal combustion engine at the time of coupling of the electromagnetic clutch when speed change gears are to be switched is maintained within a predetermined range, and correcting a relationship between the rotational speed of the internal combustion engine and the throttle opening with the use of a learning routine every speed change operation so that such control can correspond to respective conditions and dispersion in internal combustion engines, thereby mitigating a speed change shock.
A shift device disclosed in the prior art for performing gear change of a synchronous meshing type automatic transmission control system employs a pair of three-position hydraulic cylinders for actuating a shift-select lever in an axial direction and in a direction of rotation, and is designed to drive a three-position hydraulic cylinder for selection to select a shift rod and to drive a three-position hydraulic cylinder for shift to move the selected shift rod, thus performing speed change stages. Also, in addition to such hydraulic type shift device, there is generally used an electrically driven, synchronous meshing type automatic transmission control system which uses two motors to perform shift driving and select driving.
The switching action of gear stages in an electrically driven, synchronous meshing type automatic transmission control system comprises using a select actuator to select a coupling means being operated while controlling a select position by means of a positional signal of a select position sensor, and moving the coupling means by means of a shift actuator to perform coupling of a target gear while controlling a shift position by means of a positional signal of a shift position sensor, controlling an amount of driving of a shift-select actuator with a parameter being a deviation amount between an actual shift-select position detected by a shift-select position sensor and a target shift-select position to conform the shift-select position to the target position, and using an electromagnetic clutch to make transmission of power between an internal combustion engine and the synchronous meshing type automatic speed change mechanism ON/OFF in speed change operation.
In a vehicle using such synchronous meshing type automatic speed change mechanism and a clutch in transmission and shut-off of power between a crankshaft of an internal combustion engine and an input shaft of the synchronous meshing type automatic speed change mechanism, moment of inertia becomes great since gears and a driven member of the clutch are mounted on the input shaft of the synchronous meshing type automatic speed change mechanism, whereby it takes time in achieving rotational synchronization of the input shaft of the synchronous meshing type automatic speed change mechanism and an output shaft at the time of gear change, so that there is caused a problem that such time for gear change gives a driver an uncomfortable feeling to worsen a driving feeling. Also, when an action of rotational synchronization is suddenly performed in order to shorten a time of speed change for coping with such problem, there is caused a problem that noises generate from gears and a synchronizing mechanism for achieving rotational synchronization is degraded in durability.
The invention has been contemplated to solve such problems, and has its object to provide a synchronous meshing type automatic transmission control system capable of shortening a time for gear change without generation of noises from gears and degradation of a synchronizing mechanism in durability.
A synchronous meshing type automatic transmission control system according to the invention comprises a speed change mechanism coupled to an internal combustion engine on a vehicle through a clutch, a shift-select actuator for selectively coupling one set of a plurality of sets of speed change gears having different gear ratios and intervening between an input shaft of the speed change mechanism coupled to the clutch and an output shaft of the speed change mechanism for driving the vehicle, a shift-select position sensor for detecting a selected position of the shift-select actuator, and a control means for inputting thereinto an output signal of the shift-select position sensor to operate a position of the shift-select actuator for gear change and for putting the clutch in weak coupling in the case where the internal combustion engine is smaller in rotational speed than the input shaft of the speed change mechanism in a state, in which no gear is coupled between the input shaft and the output shaft in the course of gear change.
Also, according to the invention the coupling strength of the clutch put in weak coupling is set on the basis of rotational speed of the internal combustion engine, whereby it is possible to stably shorten a time for gear change irrespective of rotational speeds of the internal combustion engine and of the input shaft in the initial stage of speed change action.